Regardless of what power source
a car is using, the less its aerodynamic drag, the less energy will
be needed to travel at any given speed. A great deal of effort has
gone into designing the Insight around the goal of achieving excellent
aerodynamics, the end result being a drag coefficient of only 0.25,
the lowest achieved by any mass produced car. In comparison, the Honda
Civic Hatchback, with roughly the same 1.9 square-meter frontal area
as the Insight, has a Cd of 0.36, and needs around 32 percent more
power to operate at the same speed as the Insight.

Tapered Tear-Drop Shape

The Insight's body is tapered so that
it narrows towards the back, creating a shape that approaches the
optimal tear-drop shape. To allow the body to narrow, the rear wheel
track places the rear wheels 4.3 inches closer together than the front
wheels. The cargo area above the wheel wells is still narrower. The
floor under the rear portion of the car actually slopes upwards, while
the downward slope of the rear hatch window also contributes to an
overall narrowing of the car at the rear.

At the very back of the Insight,
the teardrop shape is abruptly cut off in what is called a Kamm back
(a distinctive design feature also shared by the Honda CRX). The Kamm
back takes advantage of the fact that beyond a certain point there
is little aerodynamic advantage to be gained by rounding off or tapering
and extending the tail section of an automobile, so one might as well
abruptly truncate it at that point. The Kamm back is a design feature
that has been incorporated into many high-performance automobiles
and racing cars over the years.

Flat under-body Covers

Another important aerodynamic detail
that greatly contributes to the Insight body's low coefficient of
drag is the careful management of underbody airflow. The Insight body
features a flat underbody design that smoothes airflow under the car,
including three plastic resin underbody covers. Areas of the underside
that must remain open to the air, such as the exhaust system and the
area around the fuel tank, have separate fairings to smooth the airflow
around them.

In order to minimize air leakage
to the underside, the lower edges of the sides and the rear of the
body form a strake that functions as an air dam. At the rear, the
floor pan rises at a five-degree -angle toward the rear bumper, creating
a gradual increase in underbody area that smoothly feeds underbody
air into the low-pressure area at the rear of the vehicle.

Note that high voltage cables that
are passed above the underbody covers, and so the covers must be replaced
if removed for any reason.

Other Aerodynamic Features

Other aerodynamic features includes:

Optimally designed air intake
shape, including shape of louvers

Aerodynamically shaped nose

Steeply raked windshield with
edges that blend smoothly with the cabin roof, and with the aerodynamically
shaped windshield posts

To improve airflow over the
exposed wheels, the aluminum wheels have a flat-faced design.

The air dams are used in front
of both front and rear wheels to improve aerodynamic characteristics.
Since these spoilers extend lower than the rest of the body, when
parking in front of concrete curb stops, you should be careful not
to drive forward too far.

The headlight assemblies blend
smoothly into the contour of the fender, and the fenders have large-radius
curves in order to minimally disturb the air flowing around them.